Color silver halide photographic materials generally contain layer units sensitive to each of the primary regions of the visible spectrum, i.e., the blue, green, and red regions, and coupler compounds. Such coupler compounds have the function of producing dyes to make up the images recorded in such materials. Usually, a yellow dye-forming coupler is associated with a blue sensitive silver halide emulsion layer, a magenta dye-forming coupler is associated with a green sensitive silver halide emulsion layer, and a cyan dye-forming coupler is associated with a red sensitive silver halide emulsion layer.
Silver halide employed in these materials has inherent sensitivity in the blue region of the visible spectrum. Increased sensitivity to blue light, along with sensitivity to green light or red light, is imparted through the use of various sensitizing dyes adsorbed on the silver halide grains. Sensitized silver halide, however, retains its intrinsic sensitivity to blue light, and, therefore, the red sensitive and green sensitive layers of color photographic elements are sensitive to radiation in the blue region of the spectrum as well as to radiation in the region of the spectrum intended to be recorded, i.e., green or red radiation, respectively.
If, prior to processing, blue light reaches a layer containing silver halide sensitized to a region of the spectrum other than blue, such exposed silver halide grains would be rendered developable, resulting in a false rendition of the image information recorded by the photographic element. It is common, therefore, to incorporate in the photographic element a material that filters blue light. This blue absorbing material can be located anywhere in the element where the filtering of blue light is desirable. In a photographic element with layers sensitized to each of the primary colors, it is common to have the blue sensitive layer closest to the exposure source and to impose a blue-absorbing, or yellow, filter layer between the blue sensitive layer and green and red sensitive layers.
Similarly, if the red layer sensitization is broad enough to respond to unwanted green light exposure, a false rendition of color is observed. In such instances, the use of a magenta filter dye residing below the green sensitive silver halide emulsion layer, but above the red sensitive layers, is advantageous. The green light is absorbed, and thus does not expose the red sensitive layers.
The material most commonly used as a blue-absorbing material in photographic elements is yellow colloidal silver, known in the art as Carey Lea silver. Carey Lea silver, however, exhibits unwanted absorption in the green region of the spectrum. Silver can also cause unwanted photographic fog. Filter dyes can provide the beneficial light absorption properties without the undesirable effects of Carey Lea silver. Examples of materials useful as filter dyes are those described in U.S. Pat. Nos. 4,420,555 to Krueger et al. and 4,923,788 to Shuttleworth et al.
There are many known classes of compounds that are useful as couplers in photographic materials. 5-Pyrazolone compounds and pyrazoloazole (e.g., pyrazolotriazole) compounds are well-known as magenta dye-forming couplers. Such couplers are described in, for example, James, The Theory of the Photographic Process, MacMillan, 1977. One type of magenta dye-forming coupler is the 4-equivalent type. With 4-equivalent couplers, a hydrogen atom is cleaved from the coupler compound at the coupling position when the compound couples with the oxidized color developer. Four moles of silver halide must be reduced in order to form one mole of dye from a 4-equivalent coupler.
A second type of magenta dye-forming coupler known in the art is the 2-equivalent type. As described below, such couplers require the reduction of two moles of silver halide to form one mole of dye.
When a 4-equivalent magenta dye-forming coupler is incorporated in a green sensitive layer adjacent to a filter layer having a certain known type of filter dye, an unacceptable increase in light-induced yellowing or "printout" of the post-processing image occurs. Therefore, a problem to be solved by this invention is a reduction in the printout increase which occurs when certain filter dyes are used in conjunction with 4-equivalent magenta dye-forming couplers. Elements of this type have been described in U.S. Pat. No. 4,923,788 to Shuttleworth et al.
Although the problem of an increase in printout is significant for both of the two major types of photographic elements, color negative and color reversal elements, it is a more serious problem with color reversal materials.
In color negative materials, the element is exposed to light and processed with a color developer that imagewise forms a silver image and a dye image. The silver image is formed due to the color developer's reduction of exposed silver halide to form silver and oxidized color developer. The dye image is formed by the reaction of oxidized color developer with dye-forming coupler. The silver image is bleached and solubilized for removal, leaving only a negative color dye image. This image is then used to expose another color negative material to form a positive color dye image.
In contrast, in reversal materials, the element is generally exposed and processed with a black-and-white developer to form a negative silver image in each layer. The remaining undeveloped silver halide thus forms a positive imagewise pattern. The undeveloped silver halide is then fogged and processed in a color developer to form a dye image along with the silver. All the silver is then bleached and solubilized for removal, leaving only the positive color dye image.
In color negative photography, the photographic element that was exposed to the image is thus used to print the finished product on a second photographic material. The effect of an unwanted increase in printout may be lessened through the use of various filters in conjunction with the printing equipment. No such masking opportunity exists with color reversal materials, because the element originally exposed to the image becomes the finished product upon processing. Any increase in printout is, therefore, more likely to be apparent in the final image with color reversal materials.